SYNOPSISThe effect of the intravenous administration of gamma globulin modified by treatment with pepsin and low pH, (I.V.G.G.), has been described. This material has been administered, as routine therapy, to 6 children with immunoglobulin abnormalities. Adequate serum IgG levels were obtained and maintained because the I.V.G.G. could be given in higher dosage than that uusally employed with the intramuscular preparation. Occurrence of untoward reactions to I.V.G.G. were observed and found to be rate dependent. Careful medical supervision is therefore essential during the entire course of the therapy.